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The Role of Tephras in Developing a High-Precision Chronostratigraphy For *Manuscript Click here to view linked References 1 The role of tephras in developing a high-precision chronostratigraphy for palaeoenvironmental reconstruction and archaeology in southern Kyushu, Japan, since 30,000 cal. BP: an integration Hiroshi Moriwakia*, Naoko Nakamurab, Toshiro Nagasakoc, David J. Lowed, Tomoe Sangawab a Emeritus Professor, Faculty of Law, Economics and Humanities, Kagoshima University, 1-21-30 Korimoto, Kagoshima, Japan 890-0065 b Research Center for Archaeology, Kagoshima University,1-21-24 Korimoto, Kagoshima, Japan 890-8580 c Faculty of Education, Kagoshima University, 1-21-30 Korimoto, Kagoshima, Japan 890-0065 d Earth Sciences, School of Science, Faculty of Science and Engineering, University of Waikato, Private Bag 3105, Hamilton, New Zealand 3204 * Corresponding author Phone: +81-995-67-0453, Fax: +81-995-67-0453 E-mail address: [email protected] (H. Moriwaki) 2 Keywords Tephrochronology, tephras, palaeoenvironment, archaeology, Late Pleistocene, Holocene, southern Kyushu, tephra lattice, INTIMATE Final MS published in Quaternary International online 4 Aug 2015 'Studies of the Quaternary in Japan' QI volume Please cite this article as: Moriwaki, H., et al., The role of tephras in developing a high-precision chronostratigraphy for palaeoenvironmental reconstruction and archaeology in southern Kyushu, Japan, since 30,000 cal. BP: an integration, Quaternary International (2016) 397, 79-92. 3 Abstract Tephras are important for the chronostratigraphy of palaeoenvironmental and archaeological records in southern Kyushu because numerous tephra beds enable these records to be connected and dated precisely using tephrochronology. A regional tephra-based framework or lattice for the past 30,000 calendar (cal.) years is proposed in the style of recent INTIMATE projects elsewhere. We review stratigraphic, compositional, age, and distributional data for a range of tephras, and comment on the relationship of several marker tephras to distinct palaeoenvironmental and cultural events in the southern Kyushu region since 30,000 cal. BP. More than 90 visible tephra beds are recorded, deriving from Kakuto, Aira, Ata, and Kikai volcanic centres, which incorporate large calderas, and the Tokara volcanic islands. The tephra record is underpinned by two widespread tephras, Aira-Tn tephra (AT; ca. 30,000 cal. BP), and Kikai-Akahoya tephra (K-Ah; ca. 7,300 cal. BP). In addition to AT and K-Ah, locally-distributed marker tephra beds are related to the chronostratigraphy of terrestrial and marine palaeoenvironments including sea-level and coastal environments, vegetation, and culture. Some tephras, notably AT, K-Ah, and Sakurajima-Satsuma tephra (Sz-S, ca. 12,800 cal. BP), have been recognized in marine and laminated lake sediments and hence dated with high precision, thereby facilitating correlation of those records to global high-resolution ice, marine, and terrestrial stratotypes. Sz-S is a useful isochron for the last deglaciation in southern Kyushu. Our integrated regional chronostratigraphic model for southern Kyushu, founded by tephras (and with further potential via systematic identification of cryptotephras), will enable change in regional palaeoenvironments and culture to 4 be evaluated in national and global contexts. 1．Introduction The past 30,000 calendar (cal.) years are notable for the occurrence of marked and abrupt environmental change during the deglaciation from the last glacial to postglacial period. Collective research efforts to integrate ice core, marine, and terrestrial records for this period have been undertaken in the North Atlantic and Australasian INTIMATE projects (INTegration of Ice-core, MArine, and TErrestrial records) to determine the nature, timing, and regional to global extent of abrupt climatic and environmental change with high precision (Alloway et al., 2007; Lowe, J. et al., 2008; Blockley et al., 2012, 2014; Davies et al., 2012; Barrell et al., 2013; Bourne et al., 2015). In Japan, such integration has not yet been conducted formally, although numerous palaeoenvironmental and archaeological records, and high-resolution records, have been accumulated (e.g. Japan Association for Quaternary Research, 2009). Such records spanning the past 30,000 cal. years have been also obtained in southern Kyushu and the surrounding area, notably the East China Sea and western Pacific Ocean (e.g. Matsushita, 2002; Moriwaki et al., 2002, 2010a, 2011; Ijiri et al., 2005). Developing high-precision palaeoenvironmental and archaeological records on a regional scale, such as in the southern Kyushu area, is a critical step towards constructing an integrated national Japanese stratotype. Tephras have played an important role for high-precision integration of regional and national-scale records in northwestern Europe (Blockley et al., 2014; Davies et al., 2014), New 5 Zealand (Lowe, D. et al., 2008; Lowe et al., 2013; Vandergoes et al., 2013), and elsewhere (e.g. see Lowe et al., 2011), because tephra layers (and cryptotephra deposits, which are glass shard and/or crystal concentrations not visible as layers in the field) provide time-parallel stratigraphic marker beds or isochrons (Lowe, 2011; Matsu‟ura et al., 2011a, 2011b; Davies, 2015). Such a comprehensive framework of volcanic events is sometimes referred to as a lattice, which combines mineralogical and geochemical signatures with well-constrained age estimates (Bourne et al., 2015). Numerous Quaternary tephra beds in southern Kyushu have provided a stratigraphic, compositional, and chronological framework or lattice for developing a high-precision chronology of both past environments and archaeological records (Moriwaki and Lowe, 2010). Nearly 100 tephra beds have been documented for the past~ 30,000 cal. years in southern Kyushu. The tephras include those erupted as part of extremely voluminous ignimbrite-generating eruptions, the Aira-Tn tephra (AT) and the Kikai-Akahoya tephra (K-Ah). In this review, we document the key tephra beds, and their compositional character, that are essential for establishing the chronostratigraphy of palaeoenviromental and archaeological records for the past 30,000 cal. years in southern Kyushu, and develop a chronology for these records incorporating tephra-based age models. In addition, we include a summary diagram that combines the tephrostratigraphic records with marine oxygen isotope changes (recorded from cores obtained from the East China Sea and western Pacific near Kyushu) with sea-level change and coastal palaeoenvironmental change, vegetation records, and archaeological records. We also integrate this tephra-based chronostratigraphic model with benchmark records from the NGRIP 6 core and its associated age model (GICC05), a coral-based sea-level curve, and a terrestrial pollen record from central Japan. 2. Tephra-based chronostratigraphic framework in southern Kyushu In southern Kyushu, which lies on a subduction zone between the Philippine Sea Plate and the Eurasian Plate, numerous Quaternary volcanoes occur aligned north to south (Fig. 1). In the northern part of this region, the volcanoes lie in and around four gigantic calderas, namely Kakuto, Aira, Ata, and Kikai calderas, forming complex volcanic centres. Tokara volcanic islands, associated with smaller calderas and stratovolcanoes, occur south of the Kikai volcanic centre (Fig. 1). These volcanoes and volcanic centres (including calderas) have produced numerous tephras in the Quaternary period, and more than 90 tephras have been erupted in the past ~30,000 cal. years (Table 1; Moriwaki, 2010). A tephrostratigraphic framework for the past ca. 30, 000 cal. years has been erected for these tephras, which provide generally high-precision markers for the stratigraphy and chronology of palaeoenvironmental and cultural events, although age and compositional data are not yet available for some of tephra beds (Fig. 2; Machida and Arai, 2003; Moriwaki and Lowe, 2010)．We document below data on selected tephras for this framework including their sources, composition, age, stratigraphic relationships, and distribution. We emphasise tephras that are related to distinct events or changes in environments and culture in antiquity. 7 The stratigraphy of the tephras can be constructed in the proximal areas near each volcanic centre, although relationships of some thin tephras with respect to the other, much thicker, eruptives can be obscure at present, particularly the thin tephras of Tokara volcanic islands (Fig. 2). The tephras generally are distributed mainly eastward from their sources because of prevailing westerlies. Several widespread tephras such as AT, K-Ah, and Sz-S help constrain the stratigraphic positions of the more locally-distributed tephras (Figs. 2 & 3). AT and K-Ah provide exceptional isochronous markers for palaeoenvironmental and cultural events in and around Japan, as well as for southern Kyushu (Machida, 2010). In addition to AT and K-Ah, many of the smaller-scale tephras provide useful markers for the palaeoenvironmental records of southern Kyushu, which, partly because of its comprehensive tephrostratigraphy, is one of the key regions in Japan for developing a high-precision, synchronised chronology for the past ca. 30,000 cal. years. Essentially, the ages of the tephras (Table 1) are based on 14C ages obtained using mainly organic material including charcoal derived from buried soils (e.g. Okuno, 2002; Okuno and Nakamura, 2003), peat and shell fragments. Known stratigraphical and archaeological relations help provide a cross-reference
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